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circuits that provide all the acTIve funcTIons for a step-down(buck) switching regulator, capable of driving a 1A load withexcellent line and load regulaTIon. These devices are availablein fixed output voltages of 3.3V, 5V, 12V, and an adjustableoutput version.This series of switching regulators is similar to the LM2595series, with addiTIonal supervisory and performance featuresadded.Requiring a minimum number of external components, theseregulators are simple to use and include internal frequencycompensation†, improved line and load specifications,fixed-frequency oscillator, Shutdown /Soft-start, error flagdelay and error flag output.The LM2598 series operates at a switching frequency of 150kHz thus allowing smaller sized filter components than whatwould be needed with lower frequency switching regulators.Available in a standard 7-lead TO-220 package with severaldifferent lead bend options, and a 7-lead TO-263 surfacemount package. Typically, for output voltages less than 12V,and ambient temperatures less than 50°C, no heat sink isrequired.A standard series of inductors (both through hole and surfacemount types) are available from several different manufacturersoptimized for use with the LM2598 series. Thisfeature greatly simplifies the design of switch-mode powersupplies.Other features include a guaranteed ±4% tolerance on outputvoltage under all conditions of input voltage and outputload conditions, and ±15% on the oscillator frequency. Externalshutdown is included, featuring typically 85 μAstandby current. Self protection features include a two stagecurrent limit for the output switch and an over temperatureshutdown for complete protection under fault conditions.
